1. Field of the Invention
The present invention relates to a micro-actuator, its manufacturing method, an optical pickup head of an optical recording/reproducing apparatus having the micro-actuator, and its manufacturing method, and more particularly, to a micro-actuator which can be bi-directionally driven, an optical pickup head of an optical recording/reproducing apparatus which can focus a focal point of an objective lens optimally on a record layer by using the bi-directional micro-actuator, and its manufacturing method.
2. Description of the Background Art
With the MEMS (Micro Electro Mechanical System) technologies advancing, a technique of design, manufacturing and application of a microstructure, a ultra-micro actuator, various ultra-micro sensors, micro optical parts, micro fluid device or the like, which was hard to be realized in the past, has been developed and commercialized.
In case of a comb-type micro-actuator using various metals such as a polycrystalline silicon, a single crystalline silicon, aluminum or nickel, a static electricity force generated from close side wall surfaces of comb fingers (comb type electrodes) is used as a driving force of the microstructure. The static electricity force has such characteristics that only attraction works between two electrodes charged by a difference in applied voltages, so the driving force of the micro-actuator is uni-directional.
Therefore, in the case of the micro-actuator, only the uni-directional driving is used, and in case where a bi-directional driving is required, the micro-actuator is disposed at both sides, which, however, results in increase of the size and weight of a system adopting the micro-actuator and degradation of response speed.
Consequently, a technique related to the bi-directional driving of the micro-actuator is in urgent need of developing.
Recently, popularization of a personal computer and generalization of a data transmission network and a mobile communication device such as personal information terminal according to advancement of a multimedia environment accompany requirement of a considerable increase in a capacity of information to be processed and stored in those devices.
In order to cope with the situation, researches are ongoing to increase a record density of an optical recording medium such as a CD or a DVD, increase a resolution of an optical pickup device, and implement small optical components.
One of the optical pickup device satisfying the requirement of the ultra-compact high density optical recording/reproducing apparatus is a slide type optical pickup head which is able to record a data on or reproduce and search a data from an optical disk.
The optical recording/reproducing apparatus and its optical pickup head will now be described with reference to FIGS. 1 and 2.
FIG. 1 is a plan view of an optical recording/reproducing apparatus in accordance with a conventional art, and FIG. 2 is a sectional view of an optical pickup head of the optical recording/reproducing apparatus in accordance with the conventional art.
As illustrated, the conventional optical recording/reproducing apparatus includes: a swing arm 10 installed rotatable at a certain angle; an actuator 11 for rotatably driving the swing arm 10 and a head 20 installed at an edge portion of the swing arm 10 and scanning a track of a disk 12 by being floated on a disk 12 by virtue of pneumatics.
The head 20 includes a converging lens 21 mounted isolated as long as a focal distance from an objective lens 30 and a slider 22 for mounting the converging lens 21.
An air-bearing surface 22a is installed at a bottom surface of the slider 22 to levitate the slider 22 on the disk 12.
At an upper side of the head 20, there are installed a reflection mirror 41 and an optical transmitting and receiving unit 40 for transmitting and receiving optical beam in order to record/reproduce information to/from the disk 12, a recording medium.
An alignment tolerance between the position of the converging lens and the air-bearing surface is a crucial factor in determining a uniformity, a reliability and a resolution of an optical information signal recorded on and reproduced from the surface of the optical disk.
The alignment tolerance includes a evenness tolerance of the slider surface, a focal distance tolerance and a tilt tolerance in forward/backward and left/right directions of SIL (Solid Immersion Lens).
In the conventional optical recording/reproducing apparatus, because the converging lens, the slider including the air-bearing surface and the objective lens are separately manufactured and assembled. Thus, an alignment tolerance can not be avoided to degrade performance of the optical recording/reproducing apparatus.
Also, manufacturing of each component depends on grinding and cutting, so that mass-production can be hardly expected and uniformity between components is degraded, and the production efficiency is so low that a cost of production increases.
Moreover, difference of thickness of a protection layer formed on the record layer of the disk, a focal distortion due to an incomplete disk smoothness, and a change in a depth of focus cause a signal degradation.